by Micronutrients are essential plant nutrients that are needed in very small quantities for plant growth and development. While macronutrients like nitrogen, phosphorus and potassium are required in large amounts, micronutrients play an equally important role in photosynthesis, enzyme function and other metabolic activities. Let us deep dive into the world of micronutrients and understand their importance for agricultural productivity.
What are Micronutrients?
Micronutrients, also known as trace elements, are mineral elements required by plants and animals in tiny amounts. They include boron (B), copper (Cu), zinc (Zn), manganese (Mn), molybdenum (Mo), chlorine (Cl), nickel (Ni) and cobalt (Co). Unlike macronutrients which are needed in relatively large quantities, micronutrients are needed in parts per million (ppm) concentrations. However, each micronutrient plays a vital physiological and metabolic role in plants. Their deficiency or toxicity can disrupt plant functions and impair crop growth and yields.
Role of Micronutrients
Micronutrients play diverse yet crucial roles in plant metabolism. Boron is involved in sugar transport, calcium utilization and cell wall structure. Copper is a cofactor for various enzymes related to respiration and photosynthesis. Zinc acts as a cofactor for over 300 enzymes and is important for protein synthesis and carbohydrate metabolism. Manganese is involved in photosynthesis and activation of several enzymes. Molybdenum is required for nitrogen fixation and nitrate reductase enzyme. Chlorine aids in osmotic adjustments and transpiration. Nickel is essential for nitrogen fixation and urease activity. Cobalt is needed for nodulation in legumes. Any deficiency of these micronutrients manifests itself through distinct visual symptoms that impair plant health and productivity.
Causes of Micronutrient Deficiencies
Several factors are responsible for micronutrient deficiencies in soils and crops:
– Low natural reserves – Certain soils are inherently low in certain micronutrients due to parent material characteristics. For example, calcareous and alkaline soils may lack zinc, iron and manganese.
– Leaching – Heavy rains and irrigation tend to leach out micronutrients from soils over time, depleting their levels. This is a major cause of deficiencies.
– High soil pH – As soil pH increases above neutral 7, availability of many micronutrients like iron, manganese, copper and zinc decreases greatly.
– Crop removals – Intensive cropping without micronutrient replenishment depletes soil reserves. High yielding crops remove micronutrients from the field.
– Soil erosion – Loss of topsoil rich in micronutrients leads to deficiencies in erosion prone agricultural lands.
– Use of high analysis fertilizers – Excessive use of macronutrient fertilizers like urea and DAP fails to replenish micronutrients, worsening their availability.
Deficiency Symptoms and Effects on Crops
Micronutrient deficiencies can cause both qualitative and quantitative losses in crops. Here are common symptoms:
– Boron deficiency causes malformed roots, buds and young shoots in vegetables. It reduces oil content in oilseeds.
– Copper deficiency leads to discoloration and twisting of new leaves. It hampers photosynthesis and lignin formation in plants.
– Zinc deficiency results in stunted growth, rosetting in cereals and dieback in fruit trees. It reduces crop maturity and yield.
– Manganese deficiency results in interveinal chlorosis in many plants similar to iron deficiency. It impairs photosynthesis.
– Molybdenum deficiency causes whitish yellow spots between veins in leaves of many crops. Legumes fail to fix nitrogen in its absence.
– Deficiencies can reduce crop yield up to 50% depending on the severity and growth stage affected. Timely correction is needed to avoid quality and quantity losses.
Managing Micronutrient Deficiencies
Various approaches are adopted to manage micronutrient deficiencies and ensure adequate availability to crops:
– Soil application of micronutrient fertilizers like zinc sulfate, borax, copper sulfate etc. ensures long term improvements. Chelated forms like EDTA are also used.
– Foliar sprays of soluble micronutrient formulations allow quick correction of visible deficiency symptoms during the crop growth period.
– Seed treatment with micronutrient solutions helps in early plant establishment and avoiding seedling mortality.
– Use of micronutrient enriched organic manures and compost sustains soil fertility levels over years without depleting them.
– Liming of acidic soils raises pH for better micronutrient solubility and availability to plants.
– Growing leguminous green manure crops helps in biological nitrogen fixation and improvement of overall soil health parameters.
– Crop rotation and inclusion of micronutrient accumulator plants in the system improves the status of deficient micronutrients over time.
– Following soil test based fertilizer recommendations ensures balanced nutrition to crops for maximizing productivity per unit area.
In conclusion, micronutrients play significant yet subtle roles in diverse physiological functions in plants. Their deficiency impairs metabolic activities and reduces both quantitative and qualitative yields from crops. Judicious soil and foliar application of micronutrients based on soil testing and deficiency symptoms is needed to boost agricultural productivity on a sustainable basis.
